Giant mega-raptors dominated Patagonia before the great extinction

Jan. 13 () –

A study led by the University of Texas at Austin offers a vision of the diversity of dinosaurs and birds in Patagonia just before the extinction of non-avian dinosaurs.

New fossils from the Late Cretaceous represent the first record of theropods – a group of dinosaurs that includes both modern birds and their closest non-avian relatives – from the Chilean part of Patagonia. The researchers’ findings include giant mega-raptors with large sickle-shaped claws and birds of the group that also includes present-day modern species.

“The fauna of Patagonia before the mass extinction was really diverse,” he said. it’s a statement lead author Sarah Davis, who completed this work as part of her doctoral studies with Professor Julia Clarke in the Department of Geological Sciences at the UT Jackson School of Geosciences. “You have your large theropod carnivores and smaller carnivores, as well as these groups of birds that coexist alongside other reptiles and small mammals.”

The study was published in the Journal of South American Earth Sciences.

Since 2017, members of Clarke’s lab have joined scientific collaborators from Chile in Patagonia to collect fossils and build a record of ancient life in the region. Over the years, researchers have found abundant plant and animal fossils from before the asteroid impact that wiped out the dinosaurs.

The study focuses specifically on theropods, whose fossils date from between 66 and 75 million years ago.

Non-avian theropod dinosaurs were mostly carnivorous and included top predators in the food chain. This study shows that in prehistoric Patagonia, these predators included dinosaurs from two groups: mega-raptors and unilagins.

MORE THAN SEVEN METERS LONG

Measuring more than seven meters long, mega-raptors were among the largest theropod dinosaurs in South America during the Late Cretaceous. The Unenlagiinos – a group with members the size of a chicken or more than 3 meters tall – were probably covered in feathers, like their close relative the velociraptor. The unenlagiinae fossils described in the study are the southernmost known case of this group of dinosaurs.

The bird fossils also belonged to two groups: the enantiornithines and the orniturines. Although already extinct, enantiornithines were the most diverse and abundant birds millions of years ago. They looked like sparrows, but with their beaks covered in teeth. The ornithurae group includes all modern birds living today. Those that lived in ancient Patagonia could resemble a goose or a duck, although the fossils are too fragmentary to be sure.

The researchers identified the theropods from small fossil fragments; to dinosaurs, above all, from teeth and fingers, and to birds, from small bone pieces. According to Davis, the shine of the enamel on the dinosaurs’ teeth helped locate them in the rocky terrain.

Some researchers have suggested that the Southern Hemisphere faced less extreme or more gradual climate changes than the Northern Hemisphere after the asteroid impact. This could have made Patagonia and other places in the Southern Hemisphere a refuge for birds, mammals and other living things that survived the extinction. Davis claims that this study can help investigate this theory by establishing a record of ancient life before and after the extinction.

Marcelo Leppe, co-author of the study and director of the Chilean Antarctic Institute, stated that these records from the past are key to understanding life as it exists today.

“We still need to know how life made its way into that doomsday scenario and gave rise to our southern environments in South America, New Zealand and Australia,” he said. “Here the theropods are still present -no longer as dinosaurs as imposing as the megaraptorids-, but as the diverse variety of birds found in the forests, swamps and marshes of Patagonia, and in Antarctica and Australia“.